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Bugfix/mitigate some <defunct> processes #316

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merged 4 commits into from Feb 26, 2024
Merged

Bugfix/mitigate some <defunct> processes #316

merged 4 commits into from Feb 26, 2024

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wtoorop
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@wtoorop wtoorop commented Feb 16, 2024

This PR handles two processes causes

  1. Where a TCP session prevents one child to exit quickly, causing the others to become because of the blocking read waiting for QUIT_SYNC_ACK that old-main sends when all the old serve children have exited.
  2. When processes take long to exit they exit after the "reload" process becomes "main" again. In server_main(), the loop starts with reaping exited children, and then a poll or ppoll starts waiting for 60 seconds. If old-main or old server childs took long to exit, they will exit during the 60 seconds poll en become . By changing the wait to 1 second, such processes are reaped at least once a second.

@wtoorop
test package for <defunct> processes
7220825 
For the case when TCP session holds one server processes alive during a reload.
The others exit and become <defunct> because of a blocking read in
server_reload().
@wtoorop
reap old-serve processed in reload process
0cad3b7
@wtoorop
netio_dispatch timeout 1 sec for fast reaping
7bd8745 
In the server_main(). To reap children that took long to exit and exited after
the initial reaping at the start of the server_main loop.
@wtoorop wtoorop mentioned this pull request Feb 16, 2024
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wtoorop
wtoorop commented Feb 16, 2024
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wcawijngaards
wcawijngaards approved these changes Feb 21, 2024
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The code looks good, when a signal comes in during the reload change over ipc, then children are reaped by the reload process. This makes them immediately close down, instead of waiting.

k0ekk0ek
k0ekk0ek approved these changes Feb 23, 2024
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tpkg/defunct.tdir/defunct.nsd.conf.in
server-count: 5
zonesdir: "."
username: ""
database: ""
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There's no database anymore. Technically, these aren't required.

@wtoorop wtoorop merged commit ead1fb3 into master Feb 26, 2024
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wtoorop added a commit that referenced this pull request Feb 26, 2024
@wtoorop
Document merge of #316 mitigations for reaping more defunct processes
845b34f
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@k0ekk0ek k0ekk0ek k0ekk0ek approved these changes

@wcawijngaards wcawijngaards wcawijngaards approved these changes

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@wtoorop @k0ekk0ek @wcawijngaards